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Jul 20, 2013
07/13

by
M. I. Katsnelson

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It is shown that a ``vacuum polarization'' induced by Coulomb potential in graphene leads to a strong suppression of electric charges even for undoped case (no charge carriers). A standard linear response theory is therefore not applicable to describe the screening of charge impurities in graphene. In particular, it overestimates essentially the contributions of charge impurities into the resistivity of graphene.

Source: http://arxiv.org/abs/cond-mat/0609026v3

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Sep 18, 2013
09/13

by
M. I. Katsnelson

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Using the Landauer formula approach, it is proven that minimal conductivity of order of $e^{2}/h$ found experimentally in bilayer graphene is its intrinsic property. For the case of ideal crystals, the conductivity turns our to be equal to $e^{2}/2h$ per valley per spin. A zero-temperature shot noise in bilayer graphene is considered and the Fano factor is calculated. Its value $1-2/\pi$ is close to the value 1/3 found earlier for the single-layer graphene.

Source: http://arxiv.org/abs/cond-mat/0606611v1

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Sep 20, 2013
09/13

by
M. I. Katsnelson

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Carbon is one of the most intriguing elements in the Periodic Table. It forms many allotropes, some being known from ancient times (diamond and graphite) and some discovered ten to twenty years ago (fullerenes, nanotubes). Quite interestingly, the two-dimensional form (graphene) has been obtained only very recently, and immediately attracted great deal of attention. Electrons in graphene, obeying linear dispersion relation, behave like massless relativistic particles, which results in a number...

Source: http://arxiv.org/abs/cond-mat/0612534v1

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Sep 19, 2013
09/13

by
M. I. Katsnelson

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Self-trapping of an electron due to its interaction with bending fluctuations in a flexible crystalline membrane is considered. Due to the dependence of the electron energy on the corrugations of the membrane, the electron can create around itself an anomalously flat (or anomalously corrugated, depending on the sign of the interaction constant) region and be confined there. Using the Feynman path integral approach, the autolocalization energy and the size of the self-trapped state (flexuron)...

Source: http://arxiv.org/abs/1010.5100v2

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Sep 18, 2013
09/13

by
M. I. Katsnelson

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Optical properties of two-dimensional massless Dirac fermions are considered by the formalism of pseudospin precession equations which provides an easy and natural semiphenomenological way to include correlation effects. It is shown that the latter are negligible, with the only assumption that the system under consideration is normal Fermi liquid. This result probably explains recent experimental data on the universal optical conductivity of graphene (Nair R. R. et al, Science 320 (2008) 1308).

Source: http://arxiv.org/abs/0809.1034v1

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Sep 23, 2013
09/13

by
M. I. Katsnelson

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Motivated by very recent studies of Coulomb drag in grahene-BN-graphene system we develop a theory of Coulomb drag for the Fermi liquid regime, for the case when the ratio of spacer thickness $d$ to the Fermi wavelength of electrons is arbitrary. The concentration ($n$) and thickness dependence of the drag resistivity is changed from $n^{-3}d^{-4}$ for the thick spacer to $n^{-1}|\ln{(nd^2)}|$ for the thin one.

Source: http://arxiv.org/abs/1105.2534v2

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Sep 22, 2013
09/13

by
M. I. Katsnelson

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Charge carriers in graphene are chiral quasiparticles ("massless Dirac fermions"). Graphene provides therefore an amazing opportunity to study subtle quantum relativistic effects in condensed matter experiment. Here I review a theory of one of these unusual features of graphene, a "pseudodiffusive" transport in the limit of zero charge carrier concentration, which is related to existence of zero-modes of the Dirac operator and to the Zitterbewegung of unltrarelativistic...

Source: http://arxiv.org/abs/1101.2542v1

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Sep 21, 2013
09/13

by
M. I. Katsnelson

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Theory of scattering of massive chiral fermions in bilayer graphene by radial symmetric potential is developed. It is shown that in the case when the electron wavelength is much larger than the radius of the potential the scattering cross-section is proportional to the electron wavelength. This leads to the mobility independent on the electron concentration. In contrast with the case of single-layer, neutral and charged defects are, in general, equally relevant for the resistivity of the...

Source: http://arxiv.org/abs/0706.1351v2

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Sep 21, 2013
09/13

by
M. I. Katsnelson

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A comment about importance of Anderson's orthogonality catastrophe for projective Quantum Monte Carlo methods.

Source: http://arxiv.org/abs/cond-mat/0508763v2

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Sep 19, 2013
09/13

by
M. I. Katsnelson

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A theory of electron states for graphene nanoribbons with a smoothly varying width is developed. It is demonstrated that the standard adiabatic approximation allowing to neglect the mixing of different standing waves is more restrictive for the massless Dirac fermions in graphene than for the conventional electron gas. For the case of zigzag boundary conditions, one can expect a well-pronounced conductance quantization only for highly excited states. This difference is related to the...

Source: http://arxiv.org/abs/cond-mat/0703190v2

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Sep 18, 2013
09/13

by
M. Auslender; M. I. Katsnelson

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A system of generalized kinetic equations for the distribution functions of two-dimensional Dirac fermions scattered by impurities is derived in the Born approximation with respect to short-range impurity potential. It is proven that the conductivity following from classical Boltzmann equation picture, where electrons or holes have scattering amplitude reduced due chirality, is justified except for an exponentially narrow range of chemical potential near the conical point. When in this range,...

Source: http://arxiv.org/abs/0707.2804v2

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Sep 18, 2013
09/13

by
M. I. Katsnelson; E. Kogan

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We consider the real-time dynamics of the Kondo system after the local probe of the charge state of the magnetic impurity. Using the exactly solvable infinite-degeneracy Anderson model we find explicitly the evolution of the impurity charge after the measurement.

Source: http://arxiv.org/abs/cond-mat/0504332v2

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Jul 20, 2013
07/13

by
M. I. Katsnelson; F. Guinea

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We study the transport through evanescent waves in graphene quantum dots of different geometries. The transmission is suppressed when the leads are attached to edges of the same majority sublattice. Otherwise, the transmission depends exponentially on the distance between leads in rectangular dots, and as a power law in circular dots. The transmission through junctions where the transmitted and reflected currents belong to the opposite valley as the incoming one depends on details of the...

Source: http://arxiv.org/abs/0804.2348v2

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Sep 18, 2013
09/13

by
P. Souvatzis; O. Eriksson; M. I. Katsnelson

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We provide a complete quantitative explanation for the anisotropic thermal expansion of hcp Ti at low temperature. The observed negative thermal expansion along the c-axis is reproduced theoretically by means of a parameter free theory which involves both the electron and phonon contributions to the free energy. The thermal expansion of titanium is calculated and found to be negative along the c-axis for temperatures below $\sim$ 170 K, in good agreement with observations. We have identified a...

Source: http://arxiv.org/abs/0707.2214v1

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Sep 21, 2013
09/13

by
M. I. Katsnelson; A. I. Lichtenstein

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A general multiband formulation of linear and non-linear optical response functions for realistic models of correlated crystals is presented. Dipole forbidden d-d optical transitions originate from the vertex functions, which we consider assuming locality of irreducible four-leg vertex. The unified formulation for second- and third-order response functions in terms of the three-leg vertex is suitable for practical calculations in solids. We illustrate the general approach by consideration of...

Source: http://arxiv.org/abs/1008.5268v1

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Jul 20, 2013
07/13

by
A. K. Zhuravlev; M. I. Katsnelson

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An accurate numerical consideration of 1D spinless fermion model with next-nearest neighbour (NNN) interactions is carried out for the electron concentrations 4/7. It is shown that depending on the parameters of the model it can be either Luttinger liquid or bipolaron liquid. In the former case competing interactions can result in a smooth behavior of one-electron distribution function at the Fermi surface with a divergence in the second derivative with respect to the quasimomentum (and not in...

Source: http://arxiv.org/abs/cond-mat/0009238v1

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10.0

Sep 19, 2013
09/13

by
V. Yu. Irkhin; M. I. Katsnelson

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Formation of magnetically ordered state in the Kondo lattices is treated within the degenerate $s-f$ exchange and Coqblin-Schrieffer models. The Kondo renormalizations of the effective coupling parameter, magnetic moment and spin excitation frequencies are calculated within perturbation theory. The results of one-loop scaling consideration of the magnetic state in Kondo lattices are analyzed. The dependence of the critical values of the bare model parameters on the type of the magnetic phase...

Source: http://arxiv.org/abs/cond-mat/9703125v1

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Jul 20, 2013
07/13

by
H. De Raedt; M. I. Katsnelson

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Motivated by recent experimental observations of size quantization of electron energy levels in graphene quantum dots \cite{ponomarenko} we investigate the level statistics in the simplest tight-binding model for different dot shapes by computer simulation. The results are in a reasonable agreement with the experiment which confirms qualitatively interpretation of observed level statistics in terms of "Dirac billiards" without taking into account many-body effects. It is shown that...

Source: http://arxiv.org/abs/0804.2758v2

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Sep 20, 2013
09/13

by
M. I. Katsnelson; A. I. Lichtenstein

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In the framework of ab initio dynamical mean field theory for realistic electronic structure calculations a new perturbation scheme which combine the T-matrix and fluctuating exchange approximations has been proposed. This method is less computationally expensive than numerically exact quantum Monte Carlo technics and give an adequate description of the electronic structure and exchange interactions for magnetic metals. We discuss a simple expression for the exchange interactions corresponding...

Source: http://arxiv.org/abs/cond-mat/0204564v1

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Sep 18, 2013
09/13

by
V. Yu. Irkhin; M. I. Katsnelson

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An interplay of the Kondo scattering and exciton effects (d-f Coulomb interaction) in the intermediate valence systems and Kondo lattices is demonstrated to lead to an essential change of the scaling behavior in comparison with the standard Anderson model. In particular, a marginal regime can occur where characteristic fluctuation rate is proportional to flow cutoff parameter. In this regime the "Kondo temperature" itself is strongly temperature dependent which may give a key to the...

Source: http://arxiv.org/abs/cond-mat/0401501v1

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Sep 18, 2013
09/13

by
D. M. Edwards; M. I. Katsnelson

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Ferromagnetism with high Curie temperature $T_c$, well above room temperature, and very small saturation moment has been reported in various carbon and boron systems. It is argued that the magnetization must be very inhomogeneous with only a small fraction of the sample ferromagnetically ordered. It is shown that a possible source of high $T_c$ within the ferromagnetic regions is itinerant electrons occupying a narrow impurity band. Correlation effects do not reduce the effective interaction...

Source: http://arxiv.org/abs/cond-mat/0605495v1

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11

Sep 18, 2013
09/13

by
V. Yu. Irkhin; M. I. Katsnelson

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Spectra of one-electron and collective excitations in narrow-band ferromagnets with unquenched orbital moments are calculated in various theoretical models. The interaction of spin and orbital excitations with conduction electrons results in the damping of the former which, however, turns out to be rather small; therefore, apart from usual spin waves, well-defined orbitons can exist. Non-quasiparticle states occur in the electron energy spectrum near the Fermi energy due to this interaction....

Source: http://arxiv.org/abs/cond-mat/0504280v2

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Sep 21, 2013
09/13

by
A. O. Anokhin; M. I. Katsnelson

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A model of alloy is considered which includes both quenched disorder in the electron subsystem (``alloy'' subsystem) and electron-phonon interaction. For given approximate solution for the alloy part of the problem, which is assumed to be conserving in Baym's sense, we construct the generating functional and derive the Eliashberg-type equations which are valid to the lowest order in the adiabatic parameter.The renormalization of bare electron-phonon interaction vertices by disorder is taken...

Source: http://arxiv.org/abs/cond-mat/9711244v1

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Sep 23, 2013
09/13

by
M. I. Katsnelson; A. I. Lichtenstein

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We present a novel approach to calculate the effective exchange interaction parameters based on the realistic electronic structure of correlated magnetic crystals in local approach with the frequency dependent self energy. The analog of ``local force theorem'' in the density functional theory is proven for highly correlated systems. The expressions for effective exchange parameters, Dzialoshinskii- Moriya interaction, and magnetic anisotropy are derived. The first-principle calculations of...

Source: http://arxiv.org/abs/cond-mat/9904428v1

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Sep 21, 2013
09/13

by
D. W. Boukhvalov; M. I. Katsnelson

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Simulation of chemical activity of corrugated graphene within density functional theory predicts an enhancement of its chemical activity if the ratio of height of the corrugation (ripple) to its radius is larger than 0.07. Further growth of the curvature of the ripples results in appearance of midgap states which leads to an additional strong increase of chemisororption energy. These results open a way for tunable functionalization of graphene, namely, depending of curvature of the ripples one...

Source: http://arxiv.org/abs/0905.2137v2

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Sep 17, 2013
09/13

by
Oleg V. Yazyev; M. I. Katsnelson

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Magnetic zigzag edges of graphene are considered as a basis for novel spintronics devices despite the fact that no true long-range magnetic order is possible in one dimension. We study the transverse and longitudinal fluctuations of magnetic moments at zigzag edges of graphene from first principles. We find a high value for the spin wave stiffness $D$ = 2100 meV \AA$^2$ and a spin-collinear domain wall creation energy $E_dw$ = 114 meV accompanied by low magnetic anisotropy. Above the crossover...

Source: http://arxiv.org/abs/0711.0207v1

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Sep 19, 2013
09/13

by
V. Yu. Irkhin; M. I. Katsnelson

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Electron spectrum of 2D and 3D antiferromagnetic metals is calculated with account of spin-fluctuation corrections within perturbation theory in the s-f exchange model. Effects of the interaction of conduction electrons with spin waves in thermodynamic and transport properties are investigated. At lowest temperatures $TT^{*}, in 2D and ``nested'' 3D systems the picture corresponds to a marginal Fermi liquid (TlnT-contributions to specific heat and nearly T-linear dependence of resistivity)....

Source: http://arxiv.org/abs/cond-mat/9912354v1

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Sep 21, 2013
09/13

by
M. I. Katsnelson; V. E. Nazaikinskii

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We compute, in topological terms, the spectral flow of an arbitrary family of self-adjoint Dirac type operators with classical (local) boundary conditions on a compact Riemannian manifold with boundary under the assumption that the initial and terminal operators of the family are conjugate by a bundle automorphism. This result is used to study conditions for the existence of nonzero spectral flow of a family of self-adjoint Dirac type operators with local boundary conditions in a...

Source: http://arxiv.org/abs/1204.2276v2

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Sep 22, 2013
09/13

by
M. I. Auslender; M. I. Katsnelson

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The effective spin Hamiltonian is constructed in the framework of the almost half-filled Hubbard model on the Cayley tree by means of functional integral technique with the use of static approximation. The system in the ground state appears to be consisting of the ferromagnetic metallic domains and the antiferromagnetic insulating one sprovided that the concentration of excess electrons (or holes) does not exceed some critical value. The connection between the Hubbard model and the {\it s-f}...

Source: http://arxiv.org/abs/0811.1293v1

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Sep 18, 2013
09/13

by
M. I. Katsnelson; A. V. Trefilov

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Slow dynamics of energy transfer between different phonon modes under the resonance conditions is considered. It may result in new effects in the inelastic and quasielastic neutron scattering spectra.

Source: http://arxiv.org/abs/cond-mat/0401453v1

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Sep 18, 2013
09/13

by
V. Yu. Irkhin; M. I. Katsnelson

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The Green's functions that determine x-ray spectra are calculated in the s-d exchange model of a saturated conducting ferromagnet in the presence of the core hole. A possibility to observe non-quasiparticle (NQP) states in the core level (x-ray absorption, emission and photoelectron) spectroscopy is demonstrated. It is shown that NQP contributions to resonant x-ray scattering spectra can be considerably enhanced by core hole effects in comparison with those to the density of states.

Source: http://arxiv.org/abs/cond-mat/0401625v2

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Sep 20, 2013
09/13

by
V. Yu. Irkhin; M. I. Katsnelson

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Peculiarities of transport properties of three- and two-dimensional half-metallic ferromagnets are investigated, which are connected with the absence of spin-flip scattering processes. The temperature and magnetic field dependences of resistivity in various regimes are calculated. The resistivity is proportional to T^{9/2} for TT*, T* being the crossover temperature for longitudinal scattering processes. The latter scale plays also an important role in magnetoresistance. The contribution of...

Source: http://arxiv.org/abs/cond-mat/0204265v1

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Sep 22, 2013
09/13

by
A. I. Lichtenstein; M. I. Katsnelson

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We discuss a general approach to a realistic theory of the electronic structure in materials containing correlated d- or f- electrons. The main feature of this approach is the taking into account the energy dependence of the electron self-energy with the momentum dependence being neglected (local approximation). In the case of strong interactions (U/W>>1 - rare-earth system) the Hubbard-I approach is the most suitable. Starting from an exact atomic Green function with the constrained...

Source: http://arxiv.org/abs/cond-mat/9707127v1

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39

Sep 22, 2013
09/13

by
V. Yu. Irkhin; M. I. Katsnelson

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The lowest-order scaling consideration of the magnetic state formation in the Kondo lattices is performed within the $s-f$ model with inclusion of anisotropy for both the $f-f$ coupling and $s-f$ exchange interaction. The Kondo renormalizations of the effective transverse and longitudinal $s-f$ coupling parameters, spin-wave frequency, gap in the magnon spectrum and ordered moment are calculated in the case of both ferro- and antiferromagnets. The anisotropy-driven change of the scaling...

Source: http://arxiv.org/abs/cond-mat/9805390v2

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29

Jul 20, 2013
07/13

by
A. K. Zhuravlev; M. I. Katsnelson

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Haldane hypothesis about the universality of Luttinger liquid (LL) behavior in conducting one-dimensional (1D) fermion systems is checked numerically for spinless fermion model with next-nearest-neighbor interactions. It is shown that for large enough interactions the ground state can be gapless (metallic) due to frustrations but not be LL. The exponents of correlation functions for this unusual conducting state are found numerically by finite-size method.

Source: http://arxiv.org/abs/cond-mat/9910189v1

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Sep 23, 2013
09/13

by
T. Low; F. Guinea; M. I. Katsnelson

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We show that when the pseudomagnetic fields created by long wavelength deformations are appropriately coupled with a scalar electric potential, a significant energy gap can emerge due to the formation of a Haldane state. Ramifications of this physical effect are examined through the study of various strain geometries commonly seen in experiments, such as strain superlattices and wrinkled suspended graphene. Of particular technological importance, we consider setup where this gap can be tunable...

Source: http://arxiv.org/abs/1012.0939v2

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Sep 20, 2013
09/13

by
M. I. Katsnelson; M. F. Prokhorova

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Anomalous quantum Hall effects in single-layer and bilayer graphene are related with nontrivial topological properties of electron states (Berry phases $\pi$ and 2$\pi$, respectively). It was known that the Atiyah-Singer index theorem guarantees, for the case of the single-layer, existence of zero-energy states for the case of inhomogeneous magnetic fields assuming that the total flux is non-zero. This leads, in particular, to appearance of midgap states in corrugated graphene and topologically...

Source: http://arxiv.org/abs/0802.1409v2

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Sep 21, 2013
09/13

by
L. Peters; M. I. Katsnelson; A. Kirilyuk

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Self consistent renormalization theory of itinerant ferromagnets is used to calculate the Curie temperature of clusters down to approximately 100 atoms in size. In these clusters the electrons responsible for the magnetic properties are assumed to be (weakly) itinerant. It is shown that the Curie temperature can be larger than in the bulk. The effect originates from the phenomenon of level repulsion in chaotic quantum systems, which suppresses spin fluctuations. Since the latter destroy the...

Source: http://arxiv.org/abs/1106.0145v1

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Jul 24, 2013
07/13

by
D. W. Boukhvalov; M. I. Katsnelson

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Defects change essentially not only electronic but also chemical properties of graphene being centers of its chemical activity. Their functionalization is a way to modify electronic and crystal structure of graphene which may be important for graphene-based nanoelectronics. Using hydrogen as an example, we have simulated a chemistry of imperfect graphene for a broad class of defects (Stone-Wales defects, bivacancy, nitrogen substitution impurity, and zigzag edges) by density functional...

Source: http://arxiv.org/abs/0807.3855v2

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Sep 19, 2013
09/13

by
M. I. Katsnelson; K. S. Novoselov

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Graphene is the first example of truly two-dimensional crystals - it's just one layer of carbon atoms. It turns out to be a gapless semiconductor with unique electronic properties resulting from the fact that charge carriers in graphene demonstrate charge-conjugation symmetry between electrons and holes and possess an internal degree of freedom similar to ``chirality'' for ultrarelativistic elementary particles. It provides unexpected bridge between condensed matter physics and quantum...

Source: http://arxiv.org/abs/cond-mat/0703374v2

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Sep 18, 2013
09/13

by
V. Yu. Irkhin; M. I. Katsnelson

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It is proven that the sum rules for X-ray magnetic dichroism (XMCD) spectra that are used to separate spin and orbital contributions to the magnetic moment are formally correct for an arbitrary strength of electron-electron interactions. However, their practical application for strongly correlated systems can become complicated due to the spectral density weight spreading over a broad energy interval. Relevance of incoherent spectral density for the XMCD sum rules is illustrated by a simple...

Source: http://arxiv.org/abs/cond-mat/0504549v2

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25

Jul 20, 2013
07/13

by
M. I. Katsnelson; A. V. Trefilov

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A microscopic picture of the ``preparation'' of a crystal to the transition to liquid state at the approach to melting temperature is proposed. Basing on simple crystallogeometric considerations and the analysis of the computational results for corresponding anharmonic characteristics an evaluation is given for the magnitude of atomic displacements leading to the appearance of close packed Bernal pseudonuclei in the solid phase. A physical meaning of the classical Lindeman criterion and the...

Source: http://arxiv.org/abs/cond-mat/9906402v1

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Sep 19, 2013
09/13

by
A. I. Lichtenstein; M. I. Katsnelson

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We present a new approach to investigate the coexistence of antiferromagnetism and d-wave superconductivity in the two dimensional extended Hubbard model within a numerically exact cluster dynamical mean-field approximation. Self-consistent solutions with two non-zero order parameters exists in the wide range of doping level and temperatures. A linearized equation for energy spectrum near the Fermi level have been solved. The resulting d-wave gap has the correct magnitude and k-dependence but...

Source: http://arxiv.org/abs/cond-mat/9911320v1

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Sep 23, 2013
09/13

by
V. Yu. Irkhin; M. I. Katsnelson

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The longitudinal and transverse nuclear magnetic relaxation rates $1/T_1(T)$ and $1/T_2(T)$ are calculated for three- and two-dimensional (3D and 2D) metallic ferro- and antiferromagnets (FM and AFM) with localized magnetic moments in the spin-wave temperature region. The contribution of the one-magnon decay processes is strongly enhanced in comparison with the standard $T$-linear Korringa term, especially for the FM case. For the 3D AFM case this contribution diverges logarithmically, the...

Source: http://arxiv.org/abs/cond-mat/9904384v3

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Sep 19, 2013
09/13

by
S. D. Hamieh; M. I. Katsnelson

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We analyze the quantum entanglement at the equilibrium in a class of exactly solvable one-dimensional spin models at finite temperatures and identify a region where the quantum fluctuations determine the behavior of the system. We probe the response of the system in this region by studying the spin dynamics after projective measurement of one local spin which leads to the appearance of the ``decoherence wave''. We investigate time-dependent spin correlation functions, the entanglement dynamics,...

Source: http://arxiv.org/abs/quant-ph/0507266v1

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Sep 23, 2013
09/13

by
M. van Schilfgaarde; M. I. Katsnelson

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Using the quasiparticle self-consistent GW (QSGW) and local-density (LD) approximations, we calculate the q-dependent static dielectric function, and derive an effective 2D dielectric function corresponding to screening of point charges. In the q-to-0 limit, the 2D function is found to scale approximately as the square root of the macroscopic dielectric function. Its value is ~4, a factor approximately 1.5 larger than predictions of Dirac model. Both kinds of dielectric functions depend...

Source: http://arxiv.org/abs/1006.2426v1

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Jul 20, 2013
07/13

by
M. I. Katsnelson; A. I. Lichtenstein

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Starting from exact expression for the dynamical spin susceptibility in the time-dependent density functional theory a controversial issue about exchange interaction parameters and spin-wave excitation spectra of itinerant electron ferromagnets is reconsidered. It is shown that the original expressions for exchange integrals based on the magnetic force theorem (J. Phys. F14 L125 (1984)) are optimal for the calculations of the magnon spectrum whereas static response function is better described...

Source: http://arxiv.org/abs/cond-mat/0406488v1

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Sep 19, 2013
09/13

by
M. I. Katsnelson; V. P. Antropov

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A spin angular gradient approximation for the exchange correlation magnetic field in the density functional formalism is proposed. The usage of such corrections leads to a consistent spin dynamical approach beyond the local approximation. The proposed technique does not contain any approximations for the form of potential and can be used in modern full potential band structure methods. The obtained results indicate that the direct 'potential' exchange in 3d magnets is rather small compared to...

Source: http://arxiv.org/abs/cond-mat/0208420v1

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17

Sep 24, 2013
09/13

by
A. I. Lichtenstein; M. I. Katsnelson

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A novel approach to electronic correlations in magnetic crystals which takes into account a dynamical many-body effects is present. In order to to find a frequency dependence of the electron self energy, an effective quantum-impurity many-particle problem need to be solved within the dynamical mean-field theory. The numerically exact QMC-scheme and the spin-polarized fluctuation exchange approximation are used for the self-consistent solution of this single-site many-particle problem. The...

Source: http://arxiv.org/abs/cond-mat/0103389v1

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24

Sep 21, 2013
09/13

by
M. I. Auslender; M. I. Katsnelson

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We consider electron self-trapping due to its interaction with order-parameter fluuctuations at the second-order phase-transition or critical point (for example, at the Curie temperature in magnetic or ferroelectric semiconductors). Using Feynman path integral approach the autolocalization energy and the size of the self-trapped state (fluctuon) are estimated. It is shown that the fluctuon states are connected with the Lifshitz tail of the electron density-of-states, the parameters of this tail...

Source: http://arxiv.org/abs/cond-mat/0508333v1